Research On Several Key Problems Of Metro Ethernet

Ethernet has been the most dominant networking solution in local area networks, and it is now expanding to the Metro Area Networks (MAN). The application of Ethernet in the MAN, named metro Ethernet, is a hot topic, which is also widely concerned by the industries. There are various metro Ethernet solutions. The native Ethernet solution is considered as one of the most competitive solutions because of its low cost. However, it faces resilience and Quality of Service (QoS) problems. Moreover, the TDM-based solution is a practical temporary solution, because the TDM infrastructures have been wildly deployed. Therefore, we mainly focus on the resilience and QoS issues in the native Ethernet solution, and circuit design issues in the TDM-based solution in this thesis. The main achievements and contributions are as follows.1. We propose a self-protected spanning tree based recovery scheme for the native Ethernet solution to protect against any single failure. It is theoretically proved that the scheme's requirements to both the number of the trees and the network topology reach the lowest bound. Moreover, simulation results show that the recovery time is about several tens of milliseconds, which meets the metro Ethernet's resilience requirement.2. We propose a fine-adjustable low-complexity rate control circuit for congestion control in the native Ethernet solution. Based on the hardware implementation oriented modifications to the token bucket algorithm, the designed rate control circuit has the following features. The rate reduction is fine-adjustable, which meets the 1% or better granularity requirement presented by IEEE 802.3ar task force. Moreover, the circuit is simple, and its area is less than 5% of the Ethernet MAC.3. We propose a distributed switching mechanism to reduce the average delay after link failure for the native Ethernet solution. Both theoretical proofs and simulation results show that the distributed switching mechanism is able to reduce the average delay after single link failure without affecting the original average delay of the working tree.4. We propose a frame granularity scheme for Ethernet over E1, which is one of the TDM-based solutions, and implement it with FPGA. Compared with the byte granularity scheme, the advantage of the frame granularity scheme is that even if only one E1 line works normally, some frames can still be tranmitted to the far end. Thus, the failed E1 links can be isolated using the network management function.5. We propose an asynchronous sampling circuit to secure the configuration of FPGA. The feature of the asynchronous sampling circuit is that its output sequence is different every time the board is powered on, and the sequence is even related with the outside conditions such as air temperature. This uncertainty prevents the possibility of cracking the system by copying the sequence.